Since the 1970's, electric equipment with an insulation medium of sulfur hexafluoride (SF6) gas has been widely used. However, due to the limitation of design, material, process and maintenance, etc., local insulation defect may exist inside the equipment. Under heat and electricity, SF6 gas and solid insulation material are decomposed continuously, such that the insulation performance is decreased and an accident even occurs. Therefore, one of the key researches of the electric power professionals is to detect a potential fault and danger inside the electric equipment at the first opportunity and decrease the accident rate.
Based on the research, when a fault appears in electric equipment with SF6, characteristic components such as SO2, SOF2, H2S, CO, HF and CF4 will be generated in the fault section. Since the hydrogen fluoride (HF) gas is generated firstly, the fault in the electric equipment can be determined by detecting the content of the HF gas.
The Gas Insulated Switchgear, i.e., GIS switch, is a combined electric equipment with an insulation medium of sulfur hexafluoride (SF6) gas. In the prior art, the method for detecting the HF gas inside the GIS switch is to obtain a gas sample at a sampling port of the GIS switch by a sampling bag and detect the content of HF in the gas sample by a corresponding detection instrument. However, since the GIS switch has a huge volume, a small internal temperature difference and a poor gas fluidity, a little gas sample obtained from the sampling port far away from the body of the electric equipment is not a representative sample, the detection result of the gas sample is not exact and hard to reflect a real state inside the GIS switch. Therefore, it is hard to detect a potential fault inside the GIS switch in time. Furthermore, since the sampling period is long (generally once in spring and once in autumn), a potential fault inside the GIS switch cannot be detected in time either.